The present invention relates to a self-destruct fuze for a mine or other explosive device carried by a spin-launched projectile and adapted to be deployed therefrom during flight. The self-destruct fuze is supplemental to the normal fuze for exploding the device on contact with a target, to prevent the deposit of duds which might injure or damage friendly troops or equipment or add to the munitions supply of the enemy.
Since approximately 1968, a high priority military requirement has existed for a system comprising a cluster (e.g. 50) of small, independently-fuzed "scatter" mines launched by a single artillery round and retro-fire-dispersed or deployed therefrom during flight of the round, by a timing means or remote control. It is essential to this concept that each mine be capable of reliable self-destruct at a predetermined time, e.g. about 2 days, after ground impact, if it has not been exploded in the normal manner. Desired characteristics of such a system are:
1. an accuracy of 43 .+-. 5 hours over a temperature range of -40.degree.F. to +145.degree.F.; PA1 2. a shelf life exceeding ten years; PA1 3. sufficiently rugged that the time delay period is unaffected by artillery delivery or ground impact shock, e.g. 20,000 G's; and PA1 4. a cost when mass produced well under $ 10.
No technique for meeting all of these requirements has been previously demonstrated. Mechanical approaches such as dashpots and clocks are low cost but fail on accuracy and/or ruggedness. Electronic approaches to date require a battery carried by each mine to continuously power a timing circuit during the 2-day period following deployment from the projectile, and no low-cost battery has been developed for this purpose.
In accordance with the present invention, a single battery is carried by the spin projectile independently of the mines, or other explosive devices carried thereby, and this battery supplies electrical power to each of the mines, during flight through a normally-open, spin-closed switch and a current limiting resistor, to charge two capacitors, one of which forms a part of an RC timing circuit, to a voltage V1. When the mines are dispersed or deployed from the projectile, the RC circuit is isolated from the battery by means of broken connections. When the mines reach the ground and their spin ceases, the RC circuit is disconnected from the mine detonator and the other capacitor, by means of a normally-open, spin-closed, voltage-responsive switch, and the capacitor of the RC circuit begins discharging through its resistor. When the voltage across the RC circuit drops to a value V.sub.2 = V.sub.1 - V.sub.S , where V.sub.S is the switching voltage of the voltage-responsive switch, that switch closes and discharges the voltage V.sub.S through the detonator, destroying the mine.